Cryoprobe system

ABSTRACT

A cryoprobe system with a vented high pressure gas supply line. Venting of the gas supply line upon cut-off of high pressure gas quickens the warming process of the cryoprobe.

FIELD OF THE INVENTION

This invention relates to cryocoolers, and to cryoprobes for use incryosurgery.

BACKGROUND OF THE INVENTION

Cryosurgical probes are used to treat a variety of diseases. Thecryosurgical probes quickly freeze diseased body tissue, causing thetissue to die, after which it will be absorbed by the body or expelledby the body or sloughed off. Cryothermal treatment is currently used totreat prostate cancer and benign prostate disease, breast tumors andbreast cancer, liver tumors and cancer, glaucoma and other eye diseases.Cryosurgery is also proposed for the treatment of a number of otherdiseases.

The use of cryosurgical probes for cryoablation of prostate is describedin Onik, Ultrasound-Guided Cryosurgery, Scientific American at 62 (Jan.1996) and Onik, Cohen, et al., Transrectal Ultrasound-GuidedPercutaneous Radial Cryosurgical Ablation Of The Prostate, 72 Cancer1291 (1993). In this procedure, generally referred to as cryoablation ofthe prostate, several cryosurgical probes are inserted through the skinin the perineal area (between the scrotum and the anus) which providesthe easiest access to the prostate. The probes are pushed into theprostate gland through previously place cannulas. Placement of theprobes within the prostate gland is visualized with an ultrasoundimaging probe placed in the rectum. The probes are quickly cooled totemperatures typically below −120° C. The prostate tissue is killed bythe freezing, and any tumor or cancer within the prostate is alsokilled. The body will absorb some of the dead tissue over a period ofseveral weeks. Other necrosed tissue may slough off through the urethra.The urethra, bladder neck sphincter and external sphincter are protectedfrom freezing by a warming catheter placed in the urethra andcontinuously flushed with warm saline to keep the urethra from freezing.

Rapid re-warming of cryosurgical probes is desired. Cryosurgical probesare warmed to promote rapid thawing of the prostate, and upon thawingthe prostate is frozen once again in a second cooling cycle. The probescannot be removed from frozen tissue because the frozen tissue adheresto the probe. Forcible removal of a probe which is frozen to surroundingbody tissue leads to extensive trauma. Thus many cryosurgical probesprovide mechanisms for warming the cryosurgical probe with gas flow,condensation, electrical heating, etc.

A variety of cryosurgical instruments, variously referred to ascryoprobes, cryosurgical ablation devices, and cryostats andcryocoolers, have been available for cryosurgery. The preferred deviceuses Joule-Thomson cooling in devices known as Joule-Thomson cryostats.These devices take advantage of the fact that most gases, when rapidlyexpanded, become extremely cold. In these devices, a high pressure gassuch as argon or nitrogen is expanded through a nozzle inside a smallcylindrical sheath made of steel, and the Joule-Thomson expansion coolsthe steel sheath to sub-freezing cryogenic temperature very rapidly.

An exemplary device is illustrated in Sollami, Cryogenic SurgicalInstrument, U.S. Pat. No. 3,800,552 (Apr. 2, 1974). Sollami shows abasic Joule-Thomson probe with a sheath made of metal, a fin-tubehelical gas supply line leading into a Joule-Thomson nozzle whichdirects expanding gas into the probe. Expanded gas is exhausted over thefin-tube helical gas supply line, and pre-cools incoming high pressuregas. For this reason, the coiled supply line is referred to as a heatexchanger, and is beneficial because, by pre-cooling incoming gas, itallows the probe to obtain lower temperatures.

Ben-Zion, Fast Changing Heating and Cooling Device and Method, U.S. Pat.No. 5,522,870 (Jun. 4, 1996) applies the general concepts ofJoule-Thomson devices to a device which is used first to freeze tissueand then to thaw the tissue with a heating cycle. Nitrogen is suppliedto a Joule-Thomson nozzle for the cooling cycle, and helium is suppliedto the same Joule-Thomson nozzle for the warming cycle. Preheating ofthe helium is presented as an essential part of the invention, necessaryto provide warming to a sufficiently high temperature. Essentially thesame system, using helium gas to warm a cryosurgical probe, injectedinto the cryosurgical probe through the same supply line andJoule-Thomson nozzle used for cooling was clearly illustrated in 1986 bySoviet scientists E. N. Murinets-Markevich, et al. in Soviet Patent SU1,217,377. Our own U.S. patent app. Ser. No. 08/685,233 (filed Jul. 23,1996), also uses Joule-Thomson warming in a system which provides forcontrol of the freeze zone at the tip of the cryoprobe.

A Joule-Thomson cryostat for use as a gas tester is illustrated inGlinka, System for a Cooler and Gas Purity Tester, U.S. Pat. No.5,388,415 (Feb. 14, 1995). Glinka also discloses use of a by-pass fromthe Joule-Thomson Nozzle to allow for cleaning the supply line, and alsomentions that the high flow of gas in the by-pass mode will warm theprobe. This is referred to as mass flow warming, because the warmingeffect is accomplished purely by conduction and convection of heat fromthe fluid mass flowing through the probe.

Various cryocoolers use mass flow warming, flushed backwards through theprobe, to warm the probe after a cooling cycle. Lamb, RefrigeratedSurgical Probe, U.S. Pat. No. 3,913,581 (Aug. 27, 1968) is one suchprobe, and includes a supply line for high pressure gas to aJoule-Thomson expansion nozzle and a second supply line for the same gasto be supplied without passing through a Joule-Thomson nozzle, thuswarming the catheter with mass flow. Longsworth, Cryoprobe, U.S. Pat.No. 5,452,582 (Sep. 26, 1995) discloses a cryoprobe which uses thetypical fin-tube helical coil heat exchanger in the high pressure gassupply line to the Joule-Thomson nozzle. The Longsworth cryoprobe has asecond inlet in the probe for a warming fluid, and accomplishes warmingwith mass flow of gas supplied at about 100 psi. The heat exchanger,capillary tube and second inlet tube appear to be identical to thecryostats previously sold by Carleton Technologies, Inc. of OrchardPark, N.Y.

Still other Joule-Thomson cryocoolers use the mechanism of flow blockingto warm the cryocooler. In these systems, the high pressure flow of gasis stopped by blocking the cryoprobe outlet, leading to the equalizationof pressure within the probe and eventual stoppage of the Joule-Thomsoneffect. Examples of these systems include Wallach, CryosurgicalApparatus, U.S. Pat. No. 3,696,813 (Oct. 10, 1973). These systemsreportedly provide for very slow warming, taking 10-30 seconds to warmsufficiently to release frozen tissue attached to the cold probe.Thomas, et al., Cryosurgical Instrument, U.S. Pat. No. 4,063,560 (Dec.20, 1977) provides an enhancement to flow blocking, in which the exhaustflow is not only blocked, but is reversed by pressurizing the exhaustline with high pressure cooling gas, leading to mass buildup andcondensation within the probe.

Each of the above mentioned cryosurgical probes builds upon prior artwhich clearly establishes the use of Joule-Thomson cryocoolers, heatexchangers, thermocouples, and other elements of cryocoolers. Walker,Miniature Refrigerators for Cryogenic Sensor and Cold Electronics (1989)(Chapter 2) and Walker & Gingham, Low Capacity Cryogenic Refrigeration,pp. 67 et seq. (1994) show the basic construction of Joule-Thomsoncryocoolers including all of these elements. The Giaque-Hampson heatexchanger, characterized by coiled finned-tube, transverse flowrecuperative heat exchanger is typical of cryocoolers. The open mandrelaround which the finned tube coil is placed is also typical ofcryocoolers.

Each of the warming mechanisms of the prior art may be classified asmass flow warming (Glinka), reverse mass flow warming (Longsworth),Joule-Thomson warming (Murinets-Markevich, Ben Zion, and Mikus), or flowblocking (Wallach). In all of these systems, flow of cooling gas issupplied through a long high pressure line, usually several feet (one ortwo meters) of tubing to connect the cryoprobe with the gas supplymanifold. When flow of cooling gas is cut off, there is a substantialvolume of high pressure cooling gas in the supply line. This gas hasonly one place to go: through the cryoprobe, and Joule-Thomson nozzle,then out of the downstream exhaust line leading from the cryoprobe. Ittakes several seconds for the pressure to dissipate through the probe,and during this dissipation the Joule-Thomson effect continues and theprobe continues cooling. This situation delays the desired warming ofthe cryoprobe and limits the control that a surgeon may exercise overthe cooling and warming of tissue.

SUMMARY

The system described below provides for more immediate stoppage of theJoule-Thomson cooling effect than is possible with mere cooling gascut-off. The system includes a vent for the cooling gas supply line. Tostop the cooling effect, the supply of cooling gas is cut off and thisvent is opened. The reservoir of high pressure gas in the supply line isthereby vented into the operating room, and therefor does not dissipatethrough the Joule-Thomson nozzle. Cooling of the probe is immediatelystopped, and warming commences as soon as the system is aligned in thewarming mode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the supply system for a Joule-Thomsoncryoprobe incorporating a vented gas supply line.

FIG. 2 is a schematic view of the supply system for a Joule-Thomsoncryoprobe incorporating a vented gas supply line in a Joule-Thomsonwarming system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view of the supply system for a Joule-Thomsoncryoprobe incorporating a vented gas supply line. The system supplies acryoprobe 1 which may be any one of the many cryoprobes used for variousforms of cryosurgery. The probe has a Joule-Thomson nozzle 2 inside aprobe outer sheath 3, and a handle 4 of convenient size. The flexibletube 5 houses gas supply line 6 which supplies high pressure coolinggas, usually nitrogen or argon, to the cryoprobe. The gas supply line isconnected to a high pressure gas supply through high pressure fitting 7.The cryoprobe has an exhaust gas pathway inside the flexible tube, whichtakes cold expanded gas from the cryoprobe to exhaust port 8 at theproximal end of the flexible tube. The exhaust port may be located nearor at the high pressure fitting.

The gas supply system starts with the tank 9 of cooling gas. The coolinggas is typically argon or nitrogen, and is typically stored at about6000 psi. The cooling gas supply line routes cooling gas through theexternal pressure regulator 10, which regulates pressure in the line to3200 psi for supply to the system. The cooling gas supply line continuesinto the manifold through high pressure fitting 11. The supply lineinside the manifold is provided with a filter 12, and internal pressureregulator 13 set at 3000 psi, and relief valve 14, a high pressuresupply valve 15, a moisture filter 16, and a second high pressure valve17 used as the operating cutoff valve. From the high pressure valve 17,the downstream portion of the high pressure supply line 6, designated asitem 6 d, is aligned to the cryoprobe through high pressure fitting 7.The system described thus far serves to supply high pressure cooling gasto the cryoprobe. The external portion 6 x of the high pressure supplyline is typically several feet long (one or two meters), and this lengthof tubing creates a reservoir of high pressure gas that is responsiblefor delay in system response when the operating cut-off valve 17 isclosed. Although the operator of the system has intended to stop thecooling operation of the cryoprobe, cooling will continue until thereservoir of high pressure gas in line 6 d and 6 x forces itself throughthe Joule-Thomson nozzle in the probe and pressure in the line isdissipated out the exhaust 8.

The vent used to clear the high pressure cooling gas supply line isconnected to the line 6 d within the manifold and downstream of theoperating cut-off valve 17. The vent comprises a solenoid operated valve18 and a pressure regulator 19. The solenoid operated valve 18 acts asthe vent when opened, providing an alternate path for the high pressuregas in supply line portions 6 d and 6 x to escape (rather than passingthrough the probe and expanding through the Joule-Thomson nozzle). Thiseliminates essentially all delay between operator commands to the systemto cease cooling and actual cessation of cooling. The pressureregulator, set nominally at 150 pounds, reduces the noise of thedischarge through the valve 18.

In use, the cryoprobe is inserted into the body or placed in contactwith the body, depending on the operation to be performed. When thecryoprobe is properly located and cooling is desired, the operator(usually a highly trained surgeon) operates the system to initiate flowof high pressure cooling gas to the cryoprobe. The first high pressuresupply valve 15 is opened to supply the system with high pressure gas,and is typically left open during the entire cryosurgical procedure. Thesecond high pressure valve, referred to here as the operating cut-offvalve 17, is opened and closed in response to commands from the operatorto initiate cooling. The commands may be manual switch operations whichprovide for direct operator control of the solenoid which operates thevalve, or the commands may be provided through software in response tooperator input through a key board, a touch pad or push buttons or anyother convenient operator interface. When the operator closes operatingcut-off valve 17, the valve 18 opens automatically to vent high pressuregas from the supply line portions 6 d and 6 x. The automatic operationof vent valve 18 may be accomplished through electro-mechanicalinterlocks between operating cut-off valve 17 and vent valve 18, ormechanical interlocks (the two valves may be combined into a singlethree way valve), or they may be accomplished through software used tocontrol the system. It should be appreciated that quick operation ofvent valve 18, immediately upon closure or operating cut-off valve 17 oreven simultaneous with closure or operating cut-off valve 17, ispreferred. The vent valve 18 automatically closes when the pressure inthe high pressure gas supply line reaches some pre-set low pressure (thepre-set pressure may be atmospheric pressure). With the vent valveclosed, the system is ready for another cooling operation.

The low pressure regulator 19 shown in FIG. 1 lowers the vented gaspressure before release from the system, thereby reducing the noisecaused by the venting process. This regulator may be omitted inenvironments where the noise of venting 3000 psi gas (a very loud honk)can be tolerated. A muffler may be used at the vent gas outlet 20 tofurther reduce vent noise.

The vent system is described in relation to the single probe shown inFIG. 1. This system is also intended for use in a cryosurgical systemwhich includes several cryosurgical probes. The system may also includea gas supply line for warming gas supply to the Joule Thomson nozzle.The vent system may be applied to each cryoprobe in the system, and maybe applied to the warming gas supply line in those systems usingJoule-Thomson warming in order to avoid delay in the cessation ofwarming.

For application to the warming portion of system is illustrated in FIG.2. The gas supply system starts with the tank 21 of warming gas. Thewarming gas is typically helium or hydrogen, and is typically stored atabout 6000 psi. The warming gas supply line 22 routes warming gasthrough the external pressure regulator 23, which regulates pressure inthe line to 3200 psi for supply to the system. The warming gas supplyline continues into the manifold through high pressure fitting 24. Thesupply line inside the manifold is provided with a filter 25, andinternal pressure regulator 26 set at 3000 psi, and relief valve 27, ahigh pressure supply valve 28, a moisture filter 29, and a second highpressure valve 30 used as the operating cutoff valve. From the highpressure valve 30, the downstream portion of the high pressure supplyline 22, designated as item 22 d, is aligned to the cryoprobe throughjunction 31 with the downstream portion of the high pressure supply line6 d, and subsequently through high pressure fitting 7. Just as in thecooling mode, the external portion 6 x of the high pressure supply lineis typically several feet long (one or two meters), and this length oftubing creates a reservoir of high pressure gas that is responsible fordelay in system response when the operating cut-off valve 30 is closed.Although the operator of the system has intended to stop the warmingoperation of the cryoprobe, warming will continue until the reservoir ofhigh pressure gas in line 6 d and 6 x forces itself through theJoule-Thomson nozzle in the probe and pressure in the line isdissipated. The operation of the solenoid operated valve 18 serves tovent the warming gas and cease warming flow in the same manner asdescribed above in relation to cessation of cooling flow.

The vent system has been described in relation to a cryosurgical systemin order to highlight its usefulness, but it may be also used in variouscryogenic systems requiring rapid cessation of cooling flow. Theindustrial applications contemplated in Ben-Zion, U.S. Pat. No.5,522,870, including material treatment and surface curing, may beimproved with the vented system described above. Thus, while thepreferred embodiments of the devices and methods have been described inreference to the environment in which they were developed, they aremerely illustrative of the principles of the inventions. Otherembodiments and configurations may be devised without departing from thespirit of the inventions and the scope of the appended claims.

What is claimed is:
 1. A cryosurgical system comprising: a Joule-Thomsoncryoprobe; a high pressure gas supply line aligned to supply gas to theJoule-Thomson cryoprobe; an operating cut-off valve operativelyconnected to the high pressure gas supply line, said valve beingoperable to supply and cut off high pressure gas to the Joule-Thomsoncryoprobe; a vent valve operatively connected to the high pressure gassupply line, said valve being operable to vent gas from the highpressure supply line immediately upon operation of the operating cut-offvalve to cut off high pressure gas to the Joule-Thomson cryoprobe; andan interlock for controlling the vent valve, said interlock operable toopen the vent valve immediately upon operation of the cut-off valve tocut off high pressure gas to the Joule-Thomson cryoprobe.
 2. The systemof claim 1 wherein the interlock is a software controlled interlock. 3.The system of claim 1 wherein the interlock is an electrical interlock.4. The system of claim 1 wherein the interlock is a mechanicalinterlock.
 5. A cryosurgical system for use in a body of a patient, saidsystem comprising: a cryoprobe comprising a closed end tube adapted forinsertion into the body of the patient and a Joule-Thomson nozzle housedwithin the tube; a high pressure gas supply line aligned to supply gasto the Joule-Thomson nozzle; an operating cut-off valve operativelyconnected to the high pressure gas supply line, said valve beingoperable to supply and cut off high pressure gas to the Joule-Thomsonnozzle; a vent valve operatively connected to the high pressure gassupply line, said valve being operable to vent gas from the highpressure supply line immediately upon operation of the operating cut-offvalve to cut off high pressure gas to the Joule-Thomson nozzle; and aninterlock for controlling the vent valve, said interlock operable toopen the vent valve immediately upon operation of the cut-off valve tocut off high pressure gas to the cryoprobe.
 6. The system of claim 5wherein the interlock is a software controlled interlock.
 7. The systemof claim 5 wherein the interlock is an electrical interlock.
 8. Thesystem of claim 5 wherein the interlock is a mechanical interlock.
 9. Acryosurgical system for use in a body of a patient, said systemcomprising: a cryoprobe comprising a closed end tube adapted forinsertion into the body of the patient and a Joule-Thomson nozzle housedwithin the tube; a high pressure gas supply line aligned to supply gasto the Joule-Thomson nozzle; an exhaust gas pathway aligned with theclosed end tube for exhausting gas from the tube after the gas haspassed through the Joule-Thomson nozzle; an operating cut-off valve inthe high pressure gas supply line, said valve being operable to supplyand cut off high pressure gas to the Joule-Thomson nozzle; a vent valvein the high pressure gas supply line, said valve being operable to ventgas from the high pressure supply line to atmospheric pressureimmediately upon operation of the operating cut-off valve to cut offhigh pressure gas to the Joule-Thomson nozzle; and an interlock forcontrolling the vent valve, said interlock operable to open the ventvalve immediately upon operation of the cut-off valve to cut off highpressure gas to the cryoprobe.
 10. The system of claim 9 wherein theinterlock is a software controlled interlock.
 11. The system of claim 9wherein the interlock is an electrical interlock.
 12. The system ofclaim 9 wherein the interlock is a mechanical interlock.